Save as much of the length of the patient’s arm as you can, because he will probably have no prosthesis. If possible, disarticulate his elbow. If you amputate higher up, a convenient place is 18 to 20 cm below his acromion. If you can leave him with a reasonable length of humerus, he can use it to hold things by gripping them against his chest. If you have to amputate very high up, even a very short stump will preserve the outline of his shoulder. If he is to have a prosthesis, don’t amputate through the lower 4 cm of his humerus, because it will be difficult to fit.
Remember that his brachial artery lies quite superficially, and is overlapped medially by his biceps.